The self-professed mastermind of the Sept. 11, 2001, terrorist attacks showed up to court in Guantanamo Bay, Cuba, on Wednesday wearing a camouflage vest after a judge ruled that the military-style garment would not disrupt the proceedings.

Khalid Sheikh Mohammed was using his attire to make a political statement, which he coupled with a monologue late in the day’s proceedings to condemn what he called prosecutors "elastic" use of national security to justify its actions.

"The government uses national security as it chooses," the Arabic-speaking Mohammed said through a translator while seated at a defense table. "Many can kill people under the name of national security and torture people in the name of national security."

Mohammed was appearing before the military commission for the third day of hearings that will set the ground rules for the trial of the 47-year-old Kuwaiti and four accused co-conspirators accused of planning and aiding hijackers who flew commercial airlines into the World Trade Center towers, the Pentagon and a field in Pennsylvania, killing 2,976 people.

All five defendants are charged with terrorism and murder and could be sentenced to death if convicted. The trial is likely more than a year away.

Fashion statement Mohammed, who has grown a long beard in detention and dyed it with henna, wore the vest over his traditional white tunic and turban. He and a co-defendant had sought to wear camouflage items at their May 5 arraignment, but that request was denied.

At the time, the commander of the Guantanamo Bay prison said the camouflage might make it harder for the military prison guards to gain control if necessary, suggesting the clothing could create confusion about telling the difference between prisoners and fellow troops.

In Tuesday’s hearing, Military Judge Army Col. James Pohl dismissed the suggestion that the more than a dozen military members in the courtroom would have any problem distinguishing the bearded defendants. But just to be sure, he specifically prohibited them from wearing any items from U.S. military uniforms.

Mohammed considers himself a prisoner of war and wanted the same right to wear a uniform as the Japanese and German troops prosecuted for war crimes after World War II, according to his lawyers.

Mohammed surprised the courtroom midway through the afternoon by raising his hand to request that the court allow him to make a statement.

Judge Pohl said defendants are not generally permitted to comment on proceedings, but then granted his request.

"This is a one-time occurrence," Pohl told the defendant after some some back-and-forth.

"We are all human beings," Mohammed said in his brief monologue. "Your blood is not made out of gold and ours is made out of water."

He said that while Americans were sad that 3,000 people were killed on Sept. 11, the U.S. government has "killed millions of people."

He urged the judge not to be persuaded by the government's "crocodile tears," and he complained that the U.S. president can "legislate" assassinations in the name of protecting Americans.

Battle over secrecyEarlier Wednesday, the court resumed hearing arguments on the admissibility of testimony that includes information about the period of detention and harsh interrogation techniques employed at secret CIA prisons, before the men's transfer to Guantanamo Bay in 2006.

Even the judge grew frustrated with Khalid Sheikh Mohammed during a hearing at Guantanamo Bay as he refused to answer his questions. NBC's Michael Isikoff reports.

The government has already acknowledged some details about the secret prisons, including the fact that Mohammed was subjected to a near-drowning technique called water-boarding 183 times, but prosecutors have said that restrictions are necessary to prevent the release of information that would reveal information about intelligence sources and methods.

ACLU attorney Hina Shamsi picked up where she left off Tuesday when court adjourned, arguing that the detention information should be part of the public record.

Shamsi said the restrictions were overly broad and intended not to protect national security so much as to prevent the public from learning more details about the harsh confinement of the defendants in the CIA's prisons overseas.

"We are aware, your honor, of no other protective order that is as radical as what the government is asking you to judicially bless here," Shamsi said.

But government prosecutor Joanna Baltes said the ACLU and other critics of the proposed rules are exaggerating the restrictions. She said the restrictions, known as protective orders, are similar to those in major terrorism cases in civilian courts.

"I think it is a very inflammatory allegation for the ACLU to come in and claim they have never seen anything like this," Baltes said.

The painstaking pre-trial hearings are intended to deal with 25 motions, many of them dealing with security rules and defendants’ rights.

On Monday, the court agreed that the defendants could not be forced to attend the pre-trial hearings.

At Wednesday’s hearings, Mohammed, who was born in Kuwait, and Ali Abdul Aziz Ali, a Pakistani, were the only two of the five who attended. Mustafa Al Hawsawi, a Saudi; and Walid Bin Attash and Ramzi Binalshibh, both from Yemen, sat this one out.

Hearings were slated to continue on Thursday morning.

The Associated Press and NBC News' Courtney Kube and Kari Huus contributed to this report.